1. Field of the Invention
The present invention generally relates to a computer and other information processing apparatus, a control method for the information processing apparatus, a multifunction peripheral and other image recording apparatus, a control method for the image recording apparatus, a program, and a computer readable storage medium. The invention more particularly relates to processing of print data including information embedding binary image data, such as copy-forgery-inhibited-pattern image data.
2. Description of the Related Art
In the field of document management and security improvement, there is a conventional technique capable of embedding a specific pattern (or sign) on a physical paper, such as a cfip (copy-forgery-inhibited-pattern) image, two-dimensional bar code image, and a digital watermark image.
For example, as discussed in Japanese Patent Application Laid-open No. 2001-197297 and Japanese Patent Application Laid-open No. 2002-002916, a printer driver of a host computer can produce cfip image data. According to the Japanese Patent Applications, an application software of the host computer can produce document data. Then, the host computer transmits the document data and the cfip image data to a printer. The printer combines the original document data and the cfip image data and outputs a printed image.
As discussed in Japanese Patent Application Laid-open No. 2001-197297, the cfip image includes a latent image and a background image which are substantially identical with each other in reflection density on a sheet (paper). However, when the sheet is copied, the reflection density of the latent image can exceed the reflection density of the background image.
To provide two images (i.e., latent image and background image) having the aforementioned relationship, the background image can be composed of numerous small dots (for example, those having a size equal to or less than 42 μm×42 μm), while the latent image can be composed of a relatively small number of large dots (for example, those having a size equal to or greater than 126 μm×126 μm).
The reproduction ability of each copying machine is generally limited. That is, it is more difficult for a copying machine to clearly reproduce small dots on a sheet when copied, compared to larger dots.
Therefore, when a copying machine copies a sheet including a cfip image, a background image constructed by small dots tends to become unclear (tends to disappear). On the other hand, the copying machine can clearly reproduce a latent image constructed by large dots.
Therefore, even though the latent image and the background image are equalized in reflection density on a sheet in an initial state, the reflection density of the latent image exceeds the reflection density of the background image when copied on a sheet.
The cfip image utilizes the aforementioned phenomenon. For example, an official resident's card obtainable from a municipal office can include a cfip image, so that a character string such as “invalid” can appear when the official resident's card is copied.
In general, the data required for forming a latent image on a sheet can be referred to as latent image data. And, the data required for forming large dots of a latent image on a sheet can be referred to as latent image pattern data. FIG. 15A shows practical latent image pattern data usable for forming a black cfip image. In the drawings, a black pixel represents a pixel having a pixel value of (R,G,B)=(0,0,0) or (C,M,Y,K)=(0,0,0,255). On the other hand, a white pixel represents a pixel having a pixel value of (R,G,B)=(255,255,255) or (C, M,Y,K)=(0,0,0,0).
Furthermore, the data required for forming a background image on a sheet can be referred to as background image data. And, the data required for forming small dots of the background image on the sheet can be referred to as background image pattern data. FIG. 15B shows practical background image pattern data usable for forming the black cfip. Similar to FIG. 15A, a black pixel has a pixel value of (R,G,B)=(0,0,0) or (C,M,Y,K)=(0,0,0,255). And, a white pixel has a pixel value of (R,G,B)=(255,255,255) or (C, M,Y,K)=(0,0,0,0).
More specifically, the cfip image data can include black cfip image data, cyan cfip image data, and magenta cfip image data. In any cfip image data, pixels constituting the cfip image data have a binary value. For example, each pixel constituting the cyan cfip image data is a cyan pixel or a white pixel. The cyan pixel has a pixel value of (R,G,B)=(0,255,255) or (C,M,Y,K)=(255,0,0,0). The white pixel has a pixel value of (R,G,B)=(255,255,255) or (C,M,Y,K)=(255,0,0,0).
The data indicating the position of dots (more specifically, having no information with respect to any intermediate color) can be referred to as binary image data. The cyan cfip image data is binary image data of cyan. The above-described black cfip image data is binary image data of black.
Furthermore, a 2-dimensional code is known as an extended code of a conventional one-dimensional bar code. The 2-dimensional code can include information of vertical and lateral directions. For example, QR Code (registered trademark) is generally known and widely used as a standardized 2-dimensional code (refer to Japanese Patent Application Laid-open No. 2002-002916).
An application of a host computer can produce 2-dimensional code data and original document data and can transmit the produced data to a multifunction peripheral. The multifunction peripheral can combine these data and produce a printed image.
The 2-dimensional code data is black-and-white binary image data. The aforementioned cfip image data, two-dimensional code data, bar code data, and digital watermark data can be collectively referred to as “information embedding binary image data.”
The following description includes technical terms defined in the following manner.
Print job data: defined as job data including tag data and print data.
Print data: indicating bit map data to be produced, and expressed in terms of page description language (PDL).
Original document data: created by an application, such as WORD (trademark) or EXCEL (trademark), and including no information embedding binary image data.
Tag data: added as additional information to print data, and including instruction such as “execute printing by 2 in 1”, “transmit print data”, and “store print data”, or message such as “print data includes information embedding binary image data.” Tag data is “an instruction to multifunction peripheral” other than the print data.
Image: existing on a sheet or a display as picture or illustration.
Image data: used for expressing an image on a sheet or a display, for example, as bit map data, wherein when specific data is defined in the concept of “image data,” appropriate leading wording corresponding to the specific data is added to the “image data,” as shown by the following examples.
Binary image data: defined as image data constituted by pixels having pixel values 0 and 255 only (when the range of the pixel value is 256).
Cfip image data: defined as bit map data used when cfip image is formed on a sheet.
Bar code data: defined as bit map data used when a bar code is formed on a sheet.
Two-dimensional code data: defined as bit map data used when a two-dimensional code is formed on a sheet.
Digital watermark data: bit map data used for forming a digital watermark on a sheet.
The multifunction peripherals are usually configured to separate print data from print job data received and convert the print data into bit map image data, and then apply lossy compression to the bit map image data. Performing the lossy compression in this manner can reduce a memory capacity to be allocated to the bit map image data. Accordingly, the remaining memory capacity can be effectively used for other processing (e.g., copy processing, storage processing, and data transmission/reception processing).
In other words, the above-described multifunction peripherals can increase a memory capacity available for the other aforementioned processing. Thus, the above-described multifunction peripherals can simultaneously execute the print processing and other processing.
Securing a sufficient amount of memory capacity available for two or more processing to be executed simultaneously also provides the following advantages.
For example, when the multifunction peripheral receives print job data including a very large page number of image data, the multifunction peripheral can smoothly process the print job data, producing lossy compressed image data and capable of storing the produced image data in a memory due to a sufficient amount of memory capacity available. As a result, the throughput of the multifunction peripheral can be improved.
As described above, the multifunction peripheral performs the lossy compression processing to reduce the data size of image data on one hand and to speedily execute two or more processing to be simultaneously performed on the other hand.
The JPEG compression is characteristic in mainly ignoring high frequency components. When a compression rate of the JPEG compression is set to high, most of high frequency components are omitted. Therefore, if the JPEG compression is applied to the binary image data containing independent dots (small regions having the density value 255), high frequency components are removed and an obtainable image will be dull. In one context, the small region is defined as, for example, a region containing a small pixel number, such as 1×1 pixel (having the size of approximately 42 um×42 um at 600 DPI), 2×2 pixels, or 3×3 pixels.
If the JPEG compression (lossy compression) is applied to binary image data, binary image data may be deteriorated severely and some of the information may possibly disappear. If information embedding binary image data deteriorates as a result of a compression process, some or all of the information associated with the embedded binary image data may be lost. If the compression rate of the JPEG compression (lossy compression) is set to very low, binary image data will not deteriorate as much. However, the size of data resulting from such JPEG compression (lossy compression) will be larger because the binary image data will include many high frequency components.
Detailed description with respect to the above-described problem will be given below with reference to latent pattern data and background pattern data.
FIG. 16A is a view illustrating dull latent pattern data resultant from lossy compression and expansion applied to the latent pattern data shown in FIG. 15A. FIG. 16B is a view illustrating dull background pattern data resulting from lossy compression and expansion applied to the background pattern data shown in FIG. 15B.
FIG. 12A is a view illustrating an example of imperfect latent pattern data obtainable from binarization processing applied to the “dull” latent pattern data shown in FIG. 16A. As understood from FIG. 12A, the data to be used for forming large dots on a sheet are undesirably converted into the data used for forming medium dots or small dots on the sheet.
FIG. 12B is a view illustrating an example of imperfect background pattern data obtainable from binarization processing applied to the “dull” background pattern data shown in FIG. 16B. As understood from FIG. 12B, the data to be used for forming small dots on a sheet are undesirably converted into the data used for forming medium dots or small dots on the sheet.
In this manner, when both the latent pattern data and the background pattern data include medium dots and small dots, the cfip image data produced from these pattern data may not be discriminated as cfip image data. Thus, when a sheet containing cfip image data printed thereon is copied, character string such as “invalid” may not appear on its duplicate.
As described with reference to the examples of cfip image data, when lossy compression is applied to binary image data, the dots may not be accurately positioned and as a result the intended information may not be properly embedded into binary image data. More specifically, in the case of cfip image data, character string may not properly appear on a duplicate in a visible state. In the case of digital watermark data, bar code, or two-dimensional code, a code reader or a watermark reader may not be able to properly read the information on a duplicate.
Therefore, it is desired to provide an information processing apparatus configured to apply lossy compression to image data so that cfip image data combined with original document data can be properly printed, and it is desired to provide a related control method for the information processing apparatus.
Furthermore, it is desired to provide an image processing apparatus configured to perform lossy compression applied to ordinary image data to simultaneous execute two or more processing or to speedily execute each processing and also configured to suppress deterioration of information relating to cfip image data (or composite image data including cfip image data and original document data). It is also desired to provide a related control method for the image processing apparatus.